package com.fengdi.book.hard.design;

import java.awt.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * public interface NestedInteger {
 *
 *     // @return true if this NestedInteger holds a single integer, rather than a nested list.
 *     public boolean isInteger();
 *
 *     // @return the single integer that this NestedInteger holds, if it holds a single integer
 *     // Return null if this NestedInteger holds a nested list
 *     public Integer getInteger();
 *
 *     // @return the nested list that this NestedInteger holds, if it holds a nested list
 *     // Return empty list if this NestedInteger holds a single integer
 *     public List<NestedInteger> getList();
 * }
 */

interface NestedInteger {
    public boolean isInteger();
    public Integer getInteger();
    public List<NestedInteger> getList();
}


public class NestedIterator implements Iterator<Integer> {
    private LinkedList<NestedInteger> list;

    public NestedIterator(List<NestedInteger> nestedList) {
        this.list = new LinkedList<>(nestedList);
    }

    @Override
    public Integer next() {
        return this.list.removeFirst().getInteger();
    }

    @Override
    public boolean hasNext() {
        while(!this.list.isEmpty() && !this.list.getFirst().isInteger()) {
            List<NestedInteger> sub = this.list.removeFirst().getList();
            for(int i = sub.size() - 1; i >= 0; i--) {
                this.list.addFirst(sub.get(i));
            }
        }
        return !this.list.isEmpty();
    }
}

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i = new NestedIterator(nestedList);
 * while (i.hasNext()) v[f()] = i.next();
 */
